我们项目使用的是 Apache的(commons-net-3.2.jar) FTPClient,但是系统偶尔会有异常,趁着刚解决完,总结一下。

日志中提示是类似

java.lang.Exception: FTP response 421 received.  Server closed connection.

上网上一查,说是FTP服务端连接数已满了,出现这种问题一般是,部分连接占用的时间太久,导致新连接获取不到,从而抛出的异常,找到问题就方便下手了(^_^);

我的思路是,既然连接会出问题,那就从这里入手,

  1. 使用FTP连接池,管理连接
  2. 初始化连接池,设置超时时间,
  3. 连接数满时,等待连接释放

我的连接池这一块采用的也是Apache的(commons-pool2-2.2.jar)GenericObjectPool,大概有一下几个类

  1. 配置类

    package com.i1stcs.mvs.utils.ftp;
    
    //FTPClient配置类
    class FTPConfig {
    
        private String host;
        private int port;
        private String username;
        private String password;
        private String encoding;
        private String workPath;
    
        private int maxTotal;
        private int maxWaitMillis;
    
        public String getHost() {
            return host;
        }
    
        public void setHost(String host) {
            this.host = host;
        }
    
        public int getPort() {
            return port;
        }
    
        public void setPort(int port) {
            this.port = port;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        public String getEncoding() {
            return encoding;
        }
    
        public void setEncoding(String encoding) {
            this.encoding = encoding;
        }
    
        public String getWorkPath() {
            return workPath;
        }
    
        public void setWorkPath(String workPath) {
            this.workPath = workPath;
        }
    
        public int getMaxTotal() {
            return maxTotal;
        }
    
        public void setMaxTotal(int maxTotal) {
            this.maxTotal = maxTotal;
        }
    
        public int getMaxWaitMillis() {
            return maxWaitMillis;
        }
    
        public void setMaxWaitMillis(int maxWaitMillis) {
            this.maxWaitMillis = maxWaitMillis;
        }
    
    }
  2. 连接池实现类
    package com.i1stcs.mvs.utils.ftp;
    
    import org.apache.commons.net.ftp.FTPClient;
    import org.apache.commons.pool2.impl.GenericObjectPool;
    import org.apache.commons.pool2.impl.GenericObjectPoolConfig;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import com.i1stcs.mvs.utils.PropertiesUtil;
    
    public class FTPPool {
    
        private static final GenericObjectPool<FTPClient> internalPool;
        private static Logger logger = LoggerFactory.getLogger(FTPPool.class);
    
        static {
            String ip = PropertiesUtil.getValue("ftp.server.ip", "");
            String userName = PropertiesUtil.getValue("ftp.server.username", "");
            String password = PropertiesUtil.getValue("ftp.server.password", "");
            String encoding = PropertiesUtil.getValue("ftp.server.encoding", "UTF-8");
            int port = PropertiesUtil.getValue("ftp.server.port", 21);
    
            int maxTotal = PropertiesUtil.getValue("ftp.server.maxTotal", 8);
            int maxWaitMillis = PropertiesUtil.getValue("ftp.server.maxWaitMillis", 30_000);
    
            FTPConfig config = new FTPConfig();
            config.setEncoding(encoding);
            config.setHost(ip);
            config.setUsername(userName);
            config.setPassword(password);
            config.setPort(port);
            config.setMaxTotal(maxTotal);
            config.setMaxWaitMillis(maxWaitMillis);
    
            GenericObjectPoolConfig poolConfig = new GenericObjectPoolConfig();
            poolConfig.setMaxTotal(config.getMaxTotal());// 不设置的话默认是8
            poolConfig.setMaxWaitMillis(config.getMaxWaitMillis());// 不设置默认无限等待
    
            internalPool = new GenericObjectPool<FTPClient>(new FTPPoolFactory(config), poolConfig);
        }
    
        /**
         * 获取资源
         *
         * @return
         */
        public static FTPClient getFTPClient() {
            try {
                return internalPool.borrowObject();
            } catch (Exception e) {
                logger.error("获取FTP连接异常:", e);
                return null;
            }
        }
    
        /**
         * 归还资源
         *
         * @param ftpClient
         */
        public static void returnFTPClient(FTPClient ftpClient) {
            try {
                internalPool.returnObject(ftpClient);
            } catch (Exception e) {
                logger.error("释放FTP连接异常:", e);
            }
        }
    
        /**
         * 销毁池子
         */
        public static void destroy() {
            try {
                internalPool.close();
            } catch (Exception e) {
                logger.error("销毁FTP数据源异常:", e);
            }
        }
    
    }
  3. 连接池工厂类
    package com.i1stcs.mvs.utils.ftp;
    
    import java.io.IOException;
    import java.net.SocketException;
    
    import org.apache.commons.net.ftp.FTP;
    import org.apache.commons.net.ftp.FTPClient;
    import org.apache.commons.net.ftp.FTPClientConfig;
    import org.apache.commons.net.ftp.FTPReply;
    import org.apache.commons.pool2.PooledObject;
    import org.apache.commons.pool2.PooledObjectFactory;
    import org.apache.commons.pool2.impl.DefaultPooledObject;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    class FTPPoolFactory implements PooledObjectFactory<FTPClient> {
    
        private static Logger logger = LoggerFactory.getLogger(FTPPoolFactory.class);
    
        private FTPConfig ftpConfig;
        private static int BUFF_SIZE = 256000;
    
        public FTPPoolFactory(FTPConfig ftpConfig) {
            this.ftpConfig = ftpConfig;
        }
    
        @Override
        public PooledObject<FTPClient> makeObject() throws Exception {
            FTPClient ftpClient = new FTPClient();
            ftpClient.setDefaultPort(ftpConfig.getPort());
            ftpClient.setConnectTimeout(30000);
            ftpClient.setDataTimeout(180000);
            ftpClient.setControlKeepAliveTimeout(60);
            ftpClient.setControlKeepAliveReplyTimeout(60);
            ftpClient.setControlEncoding(ftpConfig.getEncoding());
    
            FTPClientConfig clientConfig = new FTPClientConfig(FTPClientConfig.SYST_UNIX);
            clientConfig.setServerLanguageCode(ftpConfig.getEncoding());
            ftpClient.configure(clientConfig);
    
            try {
                ftpClient.connect(ftpConfig.getHost());
            } catch (SocketException exp) {
                logger.warn("connect timeout with FTP server:" + ftpConfig.getHost());
                throw new Exception(exp.getMessage());
            } catch (IOException exp) {
                logger.warn("connect FTP server:" + ftpConfig.getHost() + " meet error:" + exp.getMessage());
                throw new Exception(exp.getMessage());
            }
    
            int reply = ftpClient.getReplyCode();
            if (!FTPReply.isPositiveCompletion(reply)) {
                ftpClient.disconnect();
                logger.error("FTPServer refused connection");
                return null;
            }
            boolean result = ftpClient.login(ftpConfig.getUsername(), ftpConfig.getPassword());
            if (!result) {
                logger.warn("FTP server refused refused connection.");
                throw new Exception(
                        "login failed with FTP server:" + ftpConfig.getHost() + " may user name and password is wrong");
            }
            ftpClient.setBufferSize(BUFF_SIZE);
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            ftpClient.setFileTransferMode(FTP.COMPRESSED_TRANSFER_MODE);
    
            ftpClient.changeWorkingDirectory(ftpConfig.getWorkPath());
    
            return new DefaultPooledObject<FTPClient>(ftpClient);
        }
    
        @Override
        public void destroyObject(PooledObject<FTPClient> pooledObject) throws Exception {
            FTPClient ftpClient = pooledObject.getObject();
            try {
                ftpClient.logout();
                if (ftpClient.isConnected()) {
                    ftpClient.disconnect();
                }
            } catch (IOException e) {
                throw new RuntimeException("Could not disconnect from server.", e);
            }
        }
    
        @Override
        public boolean validateObject(PooledObject<FTPClient> pooledObject) {
            FTPClient ftpClient = pooledObject.getObject();
            try {
                return ftpClient.sendNoOp();//
            } catch (IOException e) {
                logger.error("Failed to validate client:", e);
                return false;
            }
        }
    
        @Override
        public void activateObject(PooledObject<FTPClient> p) throws Exception {
            // TODO Auto-generated method stub
    
        }
    
        @Override
        public void passivateObject(PooledObject<FTPClient> p) throws Exception {
            // TODO Auto-generated method stub
    
        }
    
    }
  4. FTP工具类
    package com.songyz.ftp;
    
    import org.apache.commons.net.ftp.FTPClient;
    import org.apache.commons.net.ftp.FTPFile;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    import com.i1stcs.mvs.utils.PropertiesUtil;
    
    public class FTPHelper {
        private static final Logger log = LoggerFactory.getLogger(FTPHelper.class);
    
        public static FTPCommand createDelDirCmd(String remotePath) {
            return new DeleteDirCommand(remotePath);
        }
    
        public static FTPCommand createDelFileCmd(String remoteFile) {
            return new DeleteFileCommand(remoteFile);
        }
    
        public static void execute(FTPCommand... cmds) throws Exception {
            FTPClient client = null;
            try {
                client = FTPPool.getFTPClient();
                String mode = PropertiesUtil.getValue("ftp.server.mode", "localactive");
                String workpath = PropertiesUtil.getValue("ftp.server.workpath", "./");
                for (FTPCommand cmd : cmds) {
                    client.changeWorkingDirectory(workpath);
                    if (mode.equals("localactive"))
                        client.enterLocalActiveMode();
                    else if (mode.equals("localpassive"))
                        client.enterLocalPassiveMode();
                    else
                        client.enterRemotePassiveMode();
    
                    cmd.isOK = cmd.doAction(client);
                    if (cmd.isOK == false) {
                        if (cmd.error == null || cmd.error.isEmpty()) {
                            String clsName = cmd.getClass().getName();
                            cmd.error = "execute command:" + clsName.substring(clsName.lastIndexOf("$") + 1) + " failed -- "
                                    + client.getReplyString();
                        }
                        throw new Exception(cmd.error);
                    }
                }
            } finally {
                FTPPool.returnFTPClient(client);
            }
        }
    
        public static abstract class FTPCommand {
            protected boolean isOK = false;
            protected String error = "";
    
            public abstract boolean doAction(FTPClient client);
    
            public boolean isSuccessed() {
                return isOK;
            }
    
            public String getError() {
                return error;
            }
        }
    
        static class DeleteDirCommand extends FTPCommand {
            private String remotePath;
    
            public DeleteDirCommand(String remotePath) {
                this.remotePath = remotePath;
            }
    
            @Override
            public boolean doAction(FTPClient client) {
                try {
                    FTPFile[] files = client.listFiles(remotePath);
                    if (files == null || files.length == 0)
                        return client.removeDirectory(remotePath);
    
                    for (FTPFile file : files) {
                        if (file.isDirectory())
                            deleteChildren(client, remotePath + "/" + file.getName());
                        else
                            client.dele(remotePath + "/" + file.getName());
                    }
                    return client.removeDirectory(remotePath);
                } catch (Exception exp) {
                    error = "failed to delete dirctory " + remotePath + " in FTP server because " + exp.getMessage();
                    log.warn(error, exp);
                    return false;
                }
            }
    
            private boolean deleteChildren(FTPClient client, String pathName) {
                try {
                    FTPFile[] files = client.listFiles(pathName);
                    if (files == null || files.length == 0)
                        return client.removeDirectory(pathName);
    
                    for (FTPFile file : files) {
                        if (file.isDirectory())
                            deleteChildren(client, pathName + "/" + file.getName());
                        else
                            client.dele(pathName + "/" + file.getName());
                    }
                    return client.removeDirectory(pathName);
                } catch (Exception exp) {
                    error = "failed to delete dirctory " + remotePath + "in FTP server because " + exp.getMessage();
                    log.warn(error, exp);
                    return false;
                }
            }
        }
    
        static class DeleteFileCommand extends FTPCommand {
            private String remoteFilePath;
    
            public DeleteFileCommand(String remoteFilePath) {
                this.remoteFilePath = remoteFilePath;
            }
    
            @Override
            public boolean doAction(FTPClient client) {
                try {
                    FTPFile[] files = client.listFiles(remoteFilePath);
                    if (files == null || files.length == 0)
                        return true;
                    else
                        return client.deleteFile(remoteFilePath);
                } catch (Exception exp) {
                    error = "failed to delete file " + remoteFilePath + " in FTP server because " + exp.getMessage();
                    log.warn(error, exp);
                    return false;
                }
            }
        }
    
    }

    特别提示:PropertiesUtil这个类是我自己读取配置文件的类,就不贴代码了,

    至此,大功告成!!!

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